Tray assembly



J. D. IRONS TRAY ASSEMBLY June 9, 1964 2 Sheets-Sheet 1 Filed Oct. 16, 1961 wm am W/ma 0f fl w W Z #w J m June 9, 1964 2 Sheets-Sheet 2 Filed Oct. 16, 1961 m AZ /W W a Z V p a. W m MW a f m m M J m a 6v. E55 k United States Patent 3,136,826 TRAY ASSEMBLY Jeffery D. Irons, Tulsa, Okla, assignor to Union Tank gar Company, Chicago, Ill., a corporation of New ersey Filed Oct. 16, 1961, Ser. No. 156,184 (Filed under Rule 47th) and 35 U.S.C. 118) 1 Claim. (Cl. 261-42) This invention relates in general to fluid treating and handling operations such as moisture removal, scrubbing, absorption, fractionation and distillation and the like. It relates more particularly to apparatus for controlling the flow of ascending gas and descending liquid in a contactor and deals specifically with a terminal tray construction for use in such a contractor.

An object of the invention is to provide an improved counter-current contactor.

Another object is to provide a new and improved terminal tray construction for a counter-current section of a fluid contactor.

Yet another object is to provide a terminal tray construction which aids in the development of higher overall contactor efliciency.

Still another object is to provide a terminal tray construction which incorporates means for establishing contact between descending and ascending fluids.

A further object is to provide a terminal tray construction which in effect adds a contact zone or part of a zone to a contactor.

Still a further object is to provide a terminal tray construction which includes storage space for all of the liquid normally held in the trays of the contactor section above it.

The above and other objects are realized in accordance with the present invention by providing a new and improved terminal tray construction for a fluid contactor. In brief, the invention contemplates a terminal tray construction which facilitates the discharge of ascending gas from a lower section of a contactor through a cascade of descending liquid from the section above. In addition, the construction incorporates a well of suflicient capacity to receive and store all the liquid normally found in the trays of the section above at any one time during the operation of the contactor.

The invention, both as to its organization and method of operation, taken with further objects and advantageous thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a front elevational view of portions of a counter-current contactor incorporating a terminal tray construction embodying this invention, with parts broken away,

FIGURE 2 is an enlarged view in perspective of the terminal tray construction,

FIGURE 3 is an enlarged view taken along line 3-3 of FIGURE 1, and

FIGURE 4 is a View taken along line 44 of FIG- URE 3.

Referring to the drawings and particularly to FIGURE 1, a contactor is shown generally at 10. In the countercurrent section 11 of a contactor of this type, moisture might be purged from a gas through intimate commingling of the gas with a fluid such as glycol, for example. In the interest of clearly understanding the invention, the counter-current section 11 will be described essentially in terms of moisture removal. However, it should be understood that a contact operation of this nature might be applied equally as Well to fractionation or distillation or the like and the description of a contactor utilized in moisture removal is exemplary.

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In a typical contactor, the counter-current section 11 might form the upper portion of the structure. It normally involves a series of superimposed contact zones 12, only one of which is shown here, wherein a continuously descending stream of liquid successively commingles with a continuously ascending stream of moisture laden gas. In each of the series of superimposed contact zones 12 a separate and identical purging operation takes place in which the descending liquid is circulated throughout the zone while the ascending gas passes upwardly through it and leaves a portion of its moisture behind asit rises and passes into the next contact zone.

The descending liquid passes from the top of the counter-current section 11 to the bottom of the section in successive steps, by zone. Each zone 12 includes means for receiving liquid from the zone immediately above and distributing it throughout the zone before discharging it into the zone immediately below. Any of a number of well known and conventional zone or contactor tray constructions might be utilized. The ascending gas rises through a number of widely distributed passage means in each zone 12 and commingles with the circulating liquid as it passes upwardly into the next zone where the identical operation is repeated.

The lower portion of the contactor 10, seen generally at 15, is a conventional inlet scrubber section. As such it might be set up to remove dust or other finely divided particles from the ascending stream of gas with a liquid spray. On the other hand, it might be an additional counter-current section which, for example, could be adapted to remove H S from an ascending stream of gas with a descending stream of an amine solution. In the latter case a dual purpose counter-current contactor processing a single stream of gas, for example by removing 1-1 5 from the gas in one section and moisture in another section, would obviously be provided.

Separating the upper and lower sections, 11 and 15, of the contactor 10 is a terminal tr ay assembly seen generally at 20 in FIGURE 1. The terminal tray assembly 20 is referred to as such because it forms the lower terminus of the upper section 11 of the contactor and the upper terminus of the lower section 15. The terminal tray assembly 29 forms the basis for this invention and is characteristically referred to as a hat tray.

Generally speaking, hat trays are conventional in the field. The construction of the specific hat tray assembly 20 embodying this invention departs from known principles, however, to afford unique advantages in contactor operation and add considerably to the efiiciency of the process.

In essence, liquid descending from the lowermost contact zone 12 in the upper section 11 is deposited on a fiat member supported substantially above the floor of the terminal or hat tray assembly 20. The liquid proceeds to spill over peripheral structure on the flat member and descends in a substantially conical sheet into a well or reservoir of liquid on the floor of the zone. At the same time, ascending gas from the lower section 15 passes upwardly through the floor of the hat tray assembly within the generally conical sheet of liquid descending toward the floor. To reach conventional outlet means into the contact zone 12 immediately above the hat tray assembly 20, the gas must pass outwardly through the descending sheet of liquid and in doing so it commingles with and consequently contacts the liquid.

The result is to effectually incorporate a contact stage in a hat tray construction and consequently add what amounts to approximately one half of a conventional contact zone to the contactor operation in the same amount of space. Obviously, this proportionally increases the efiiciency of the contact operation.

The floor of the hat tray assembly 20 is defined by a partition or tray 25 secured in fluid tight relationship around its periphery to the inner surface of the cylindrical wall of contactor 10. The tray 25 might be secured to the wall by welding, for example. Generally centrally disposed of the tray is a relatively large aperture 26 and secured in fluid tight relationship to the tray surrounding the aperture is a vertically extending chimney pipe 27 which is preferably cylindrical in configuration. The chimney pipe 27 might also be welded to the partition or tray 25.

Referring now to FIGURES 3 and 4, it will be seen that the upper edge 28 of chimney pipe 27 has a trio of brackets 29 extending up from it and secured to the outer surface of the chimney pipe, also by welding, for example. These brackets 29 support a hat member, seen generally at 30. The hat member 30 is supported by the brackets 29 in such a manner that a substantial gap is left between the upper edge 23 of the chimney pipe 27 and the hat member 30.

The hat member 38 includes a lid 33 which rests on and is rigidly secured to each of the three brackets 29. It might be again secured by any conventional means such as welding. Extending upwardly from the periphery of the lid 33 and preferably welded to it is an annular weir 34. A wet wall 35 surrounds the weir 34 in engagement with the weir and might be tack welded to the outer surface of the weir. The perforations 35 in the wet wall 35 are sized such that gas and liquid both readily pass through them. The weir 34 extends a predetermined distance above the lid 33.

The predetermined distance which weir 34 extends above the lid 33 is slightly greater than the height of the liquid inlet port 38 formed in the bottom of downcomer pipe 39. This relationship is significant and will be subsequently more fully discussed. The downcomer pipe 39 is secured by welding or the like to the upper surface of lid 33 and depends from the contact zone 12 immediately above the hat tray assembly 26.

As was previously pointed out, the lower section 15 of the tower might be an inlet scrubber section of any well known construction. In such case, its primary purpose is normally to clean or scrub impurities from an ascending stream of natural gas, for example, by passing the ascending gas upwardly through a liquid spray. The liquid spray might in some instances be water in which case it could remove dust, for example, from the ascending gas or other liquid sprays might be used for other purposes. The function of such a scrubber is well known and does not form any specific part of this invention.

The gas to be treated in the tower it) enters the tower initially at the lower end of the scrubber section through gas inlet port 45. As it ascends through the scrubber section 15, it is treated by a liquid spray which enters the scrubber section through liquid inlet port 46. This liquid is removed from the lower end of the scrubber section 15, as at outlet port 47, and might be recirculated through conventional cleansing apparatus whereupon it is passed through the scrubber section again from top to bottom. After being treated in the scrubber section the gas enters the terminal tray or hat tray assembly 2%) through the chimney pipe 27.

At the same time, of course, gas is being treated in the counter-current contact section 11 of the tower 10 above the hat tray assembly 20. As has been pointed out, the countercurrent contact section 11 contains a series of superimposed contact zones 12 which might be defined by any well known type of contactor tray. Liquid normally enters the counter-current contact section 11 at liquid inlet port 59 and circulates through the uppermost zone 2 in the tower while gas ascends through the circulating liquid. In this operation the gas might be purged of moisture by glycol, for example, although this is merely an example. In succession, then, the liquid descends from zone to zone through a plurality of such zones and eventually emerges from the lowermost contact zone 12 into the downcomer pipe forming the inlet for the hat tray assembly 29.

We now have gas entering the bottom of the hat tray assembly 20 while liquid enters the hat tray assembly from the top. Of course, it will be understood that the whole of the contactor operation is continuous and gas would normally be passing upwardly through the entire contactor at all times while liquid similarly would be passing downwardly through each section of the tower at all times. However, in the interests of understanding the invention more clearly, the circulation of gas and liquid is best described independently as it has been in this discussion.

Referring now to FIGURE 4, liquid pouring out of the counter-current contact zone 12 immediately above the hat tray assembly 20 descends through the downcomer pipe 39, out of the pipe through port 3 3 and onto the surface of the lid 33 of hat member The level of liquid held on the lid 33 on the hat member 33 is estab lished by the height of the weir 34 which, as was previously pointed out, extends higher above the lid 33 than the upper edge of the liquid inlet port As liquid pours down the downcomer pipe and onto the lid 33, the level of liquid on the hat member 39 rises over the upper edge of the weir and consequently pours downwardly through sieve holes 35 along the surface of the wet wall 35, in and out of the lower sieve holes and descends in a generally cylindrical cascade to the floor of the hat tray assembly 20 defined by the partition 25. The liquid subsequently departs the contactor 10 through an outlet port 51 and is recirculated in a conventional manner to the inlet port 50.

At the same time that the liquid is descending in the foregoing manner, the ascending gas which has entered the chimney pipe 27 at its lowermost extremity, as was previously pointed out, rises up through the chimney pipe and passes outward from it beneath the hat member 30. In order to escape from the cover afforded the chimney pipe 27 by the hat member 30 the gas must either pass through sieve holes 36, over and through which descending liquid is pouring, or out from under the lowermost end of the wet wall 35 through a descending cascade of liquid. In passing through the descending liquid by taking either of the aforedescribed paths a substantial amount of commingling of the ascending gas and descending liquid is effected and a substantial amount of contact of the ascending gas by the liquid obviously results.

After the gas has passed outwardly through the de scending liquid it rises to the contact zone 12 immediately above the hat tray assembly 20 and passes into the contact zone in any of a number of well known ways, such as through bubble caps, for example. Due to the fact that the level of liquid on lid 33 is higher than the upper edge of inlet port 38, the ascending gas cannot short cut its proper route up to the contact zone immediately above. The level of the liquid is, of course, established by the height of weir 34. At the same time the descending liquid departs the floor of the hat tray assembly 20 as described by the partition 25 through liquid outlet port 50, as seen in FIGURE 1. The outlet port is set slightly above the partition 25 so that a certain amount of liquid is in the well of the hat tray assembly 20 at all times.

It will readily be seen that a substantial amount of commingling and consequently contact between the ascending gas and the descending liquid is effected in the hat tray assembly 20 by virtue of the unique construction utilized in this invention. In practice it has been found that a hat tray assembly constructed along the lines described provides as much contact as one-half of a conventional contact tray assembly itself. In other words, though a hat tray assembly is conventionally a terminal section for a countencurrcnt contactor and nothing more, this invention makes the hat tray assembly a contact zone forming assembly as well and consequently adds considerably to the overall contactor efiiciency without increasing the size of the tower and at a minimum cost.

The efliciency of a counter-current contactor might be increased by as much as or percent or more, for ex ample, through the utilization of a hat tray assembly such as has been described. This, of course, is a highly desirable result.

This hat tray construction serves another vital purpose also. A relatively deep well is formed around the chimney pipe 27, above the partition 25 and within the walls of the tower 10. This provides a storage area for a substantial amount of liquid which, as will be seen, is significant.

In normal operation, when a contactor such as the contactor 10 is shut down, a substantial amount of liquid remains in each of the trays defining the contact zones 12. It is conventional to provide weep holes in the weirs on each of these contact trays so that the liquid will slowly seep out of the trays and descend into the lowermost portion of the countercurrent section. Obviously, this liquid eventually all reaches the hat tray assembly 20.

In the hat tray assembly the well provided above the floor of the assembly, as defined by the partition 25, is suficiently large to store all this liquid above the normal operating level of the liquid and below the top of the chimney pipe 27. Consequently no liquid ever spills into the lower scrubber section 15 and no control tank to handle overflow is required. Of course, in the largest contactors, such overflow control tanks must be used, since sufficient well area cannot be provided.

This new hat tray construction adds substantially to the performance of a contactor. Since the driving forces for mass transfer of moisture in the gas, for example, are highest at point of entry, an efiicient contact operation is effected in the hat tray assembly. Unlike similar terminal tray assemblies presently utilized, this assembly aids in performing the function for which a contactor is designed; it is not dead weight, so to speak.

Increased efliciency, of course, means higher production and less expense. Savings are substantial since this hat tray construction in essence adds the equivalent of approximately one-half of a contact zone to the contactor itself.

Though a single embodiment of this invention has been described, however, it should be recognized that additional embodiments, modifications and variations thereon might fall within its purview. Consequently the scope of the invention should be limited only by the scope of the appended claim.

What is desired to be claimed and secured by Letters Patent of the United States is:

A countercurrent contactor for providing increased fluid contact eficiency, comprising; a lower contact portion for treating an ascending gas in a first predetermined manner, and an upper contact portion for subsequently treating the same ascending gas in a second and ditlerent predetermined manner, said upper contact portion having a series of vertically displaced contact zones, a terminal tray assembly between the lowermost of said contact zones and said lower contact portion, downcomer means for conducting descending liquid from said lowermost contact zone to said terminal tray assembly, said terminal tray assembly including a partition defining its floor, a chimney pipe inlet for gas extending upwardly through said partition, a lid member overlying the discharge port of said chimney pipe and supported therefrom in spaced relationship, a weir surrounding said lid member and forming a fluid tight basin on top of said lid member, a sleeve surrounding said weir and extending both above and below said weir, said sleeve having spaced perforations therein extending both above and below said Weir, liquid descending from said lowermost zone being deposited on said lid member from said downcomer means and cascading over said weir and down said perforated member around said discharge port, ascending gas from said lower contact portion being discharged from said discharge port and passing through said perforations and the liquid cascade so as to commingle with the liquid, whereby a contact process is effected and the equivalent of approximately one half of a contact zone is added to said upper contact portion of the contactor, and a relatively deep well defined below said sleeve and above said partition, said well being sufliciently large to hold all the liquid retained in the contact zones of said upper contact portion at any one time.

References Cited in the file of this patent UNITED STATES PATENTS 537,509 Wardle et a1 Apr. 16, 1895 651,190 Ilges June 5, 1900 1,776,589 Keith Sept. 23, 1930 1,806,090 Seguy May 19, 1931 1,857,351 Burhorn May 10, 1932 2,810,562 Eld et al Oct. 22, 1957 3,028,151 Kittel Apr. 3, 1962 FOREIGN PATENTS 844,371 Great Britain Aug. 10, 1960 

